Biology subjects

Sakai, H.

Publications and source records attributed to Sakai, H..

21 records · Page 2Linked to original sources

bioRxiv2019

Genetic factor for twisting legume pods identified by fine-mapping of shattering-related traits in azuki bean and yard-long bean

Legumes have evolved a unique manner of seed dispersal in that the seed pods explosively split open with helical tension generated by sclerenchyma on the endocarp. During domestication, azuki bean (Vigna angularis) and yard-long bean (Vigna unguiculata cv-gr. Sesquipedalis) have reduced or lost the sclerenchyma and lost the shattering behavior of seed pods. Here we performed fine-mapping with back-crossed populations and narrowed the candidate genomic region down to 4 kbp in azuki bean and 13 kbp in yard-long bean. Among genes located in these regions, we found MYB26 genes encoded truncated proteins in both the domesticated species. We also found in azuki bean and other legumes that MYB26 is duplicated and only the duplicated copy is expressed in seed pods. Interestingly, in Arabidopsis MYB26 is single copy and is specifically expressed in anther to initiate secondary wall thickening that is required for anther dehiscence. These facts indicated that, in legumes, MYB26 has been duplicated and acquired a new role in development of pod sclerenchyma. However, pod shattering is unfavorable phenotype for harvesting and thus has been selected against by human.

genetics↗

bioRxiv2018

High-dimensional single-cell cartography reveals novel skeletal muscle resident cell populations

Adult tissue repair and regeneration require the activation of resident stem/progenitor cells that can self-renew and generate differentiated progeny. The regenerative capacity of skeletal muscle relies on muscle satellite cells (MuSCs) and their interplay with different cell types within the niche. Yet, our understanding of the cells that compose the skeletal muscle tissue is limited and molecular definitions of the principal cell types are lacking. Using a combined approach of single-cell RNA-sequencing and mass cytometry, we precisely mapped the different cell types in adult skeletal muscle tissue and highlighted previously overlooked populations. We identified known functional populations, characterized their gene signatures, and determined key markers. Among the ten main cell populations present in skeletal muscle, we found an unexpected complexity in the interstitial compartment and identified two new cell populations. One express the transcription factor Scleraxis and generate tenocyte-like cells. The second express smooth muscle and mesenchymal cell markers (SMMCs). While distinct from MuSCs, SMMCs are endowed with myogenic potential and promote MuSC engraftment following transplantation. Our high-dimensional single-cell atlas uncovers principles of an adult tissue composition and can be exploited to reveal unknown cellular sub-fractions that contribute to tissue regeneration.

cell biology↗

bioRxiv2017

Comparison of multiple transcriptomes exposes unified and divergent features of quiescent and activated skeletal muscle stem cells

BackgroundSkeletal muscle stem cells (MuSCs) are quiescent in adult mice and can undergo multiple rounds of proliferation and self-renewal following muscle injury. Several labs have profiled transcripts of myogenic cells during developmental and adult myogenesis with the aim of identifying quiescent markers. Here, we focused on the quiescent cell state and generated new transcriptome profiles that include subfractionations of adult MuSC populations, and an artificially induced prenatal quiescent state, to identify core signatures for quiescent and proliferating MuSCs.\n\nMethodsComparison of available data offered challenges related to the inherent diversity of datasets and biological conditions. We developed a standardized workflow to homogenize the normalization, filtering, quality control steps for the analysis of gene expression profiles allowing the identification up- and down-regulated genes and the subsequent gene set enrichment analysis. To share the analytical pipeline of this work, we developed Sherpa, an interactive Shiny server that allows multiscale comparisons for extraction of desired gene sets from the analysed datasets. This tool is adaptable to cell populations in other contexts and tissues.\n\nResultsA multiscale analysis comprising eight datasets of quiescent MuSCs had 207 and 542 genes commonly up- and down-regulated, respectively. Shared up-regulated gene sets include an over-representation of the TNFa pathway via NFKb signaling, Il6-Jak-Stat3 signaling, and the apical surface processes, while shared down-regulated gene sets exhibited an over-representation of Myc and E2F targets, and genes associated to the G2M checkpoint and oxidative phosphorylation. However, virtually all datasets contained genes that are associated with activation or cell cycle entry, such as the immediate early stress response genes Fos and Jun. Empirical examination of fixed and isolated MuSCs showed that these and other genes were absent in vivo, but activated during procedural isolation of cells.\n\nConclusionsThrough the systematic comparison and individual analysis of diverse transcriptomic profiles, we identified genes that were consistently differentially expressed among the different datasets and common underlying biological processes key to the quiescent cell state. Our findings provide impetus to define and distinguish transcripts associated with true in vivo quiescence from those that are first responding genes due to disruption of the stem cell niche.

cell biology↗